SR 70 begins at the Tennessee state line in the valley formed by Blackwater Creek.

It follows that creek past Blackwater, but soon leaves it to ascend Powell Mountain, which it crosses at Hunter Gap.

From there it heads north across a relatively flat area, ending at US 58 in the eastern part of Jonesville.

was formed in the early 1950s, and replaced all of SR 70 east of Jonesville, truncating it to its current length.

[11][12] It was added back to the primary system in 1962, after being reconstructed, including the building of a new bridge over the Powell River.